LEC 3 - MCB 102 Professor Buchanan 3/2/09 Lecture 17 ASUC...

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MCB 102 Professor Buchanan 3/2/09 Lecture 17 ASUC Lecture Notes Online is the only authorized note-taking service at UC Berkeley. Do not share, copy or illegally distribute (electronically or otherwise) these notes. Our student-run program depends on your individual subscription for its continued existence. These notes are copyrighted by the University of California and are for your personal use only. D O N O T C O P Y Sharing or copying these notes is illegal and could end note taking for this course. INTRODUCTION Good morning, everyone. This is the 3 rd lecture, and the last time we’ll cover glycolysis. We started with types of metabolic pathways, prosthetic groups, carbohydrates, fates of glucose, and the ten steps of glycolysis. You can see the glycolytic pathway well in figure 16-3, with the enzymes and intermediates in the pathways. One key enzyme reaction that you should be familiar with is glyceraldehydes-3-phosphate dehydrogenase . What we see in the textbook is that we start with the enzyme with a bound NAD. The S- is a thiol form, and the SH form is a sulfhydryl group. The formation of enzyme-substrate complex occurs, and the active sulfur forms a covalent thiohemiacetal linkage with the substrate via the Cys residue. The enzyme-substrate intermediate is bound to the enzyme, and the NADH oxidizes the carbonyl to an acid anhydride. That’s then cleaved into 1,3-biphosphoglycerate, and a fresh NAD+
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MCB 102 ASUC Lecture Notes Online: Approved by the UC Board of Regents 3/2/09 D O N O T C O P Y Sharing or copying these notes is illegal and could end note taking for this course. 2 binds to the enzyme. I will touch base with you again on this diagram. Another important concept is metabolic channeling . It’s a very simple concept. Certain enzymes form a complex so that the metabolite’s intermediate doesn’t need to go in solution, so it passes from one protein to another protein. This is so the substrate is processed efficiently. The sequential action of two separate enzymes diffuses to the second enzyme. In substrate channeling, however, through a functional complex of two enzymes, the intermediate is never released in the solvent. The last figure for this lecture 2 is glycolysis, the overall balance sheet . We’ll see frequently that when a carbon substrate is not fully oxidized, only part of the energy is available for that cell. So the organism is not as successful as its aerobic counterparts. The overall balance sheet shows breakdown of one glucose molecule to form 2 pyruvate, 2 NADH, and 2 ATP. If we calculate the efficiency of that, we see that the net Gibbs free energy change is -85 kJ/mol, or 3% of the energy of
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This note was uploaded on 05/07/2009 for the course MCB 58168 taught by Professor Thorner during the Spring '09 term at University of California, Berkeley.

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LEC 3 - MCB 102 Professor Buchanan 3/2/09 Lecture 17 ASUC...

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